How it works

TireFlows

Get diameter, speedometer impact, and alternate sizes — free, no signup.

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.87%

Safety Rating

Safe

Within the recommended 3% safety margin.

The 3% rule is a common reference — not vehicle-specific advice. How it works

Speedometer Error

1.87%

Absolute Difference

0.55"

Speedometer

Assumes Tire 1 is what the speedometer is calibrated for. Shows approximate actual speed if you switch to Tire 2.

Reading (mph)Actual (mph)Difference
2020.4+0.4
3030.6+0.6
4040.7+0.7
5050.9+0.9
6061.1+1.1
7071.3+1.3
8081.5+1.5
Tire 1Dia. 29.40 ″Rim 17 ″6.20 ″Width 8.86 ″Revs/Mile 686.0Circum. 92.4″Tire 2Dia. 29.95 ″Rim 17 ″6.48 ″Width 9.25 ″Revs/Mile 673.3Circum. 94.1″
Tire 1
Specification
Tire 2
29.4"
Diameter
29.95"
8.86"
Width
9.25"
6.2"
Sidewall
6.48"
92.368"
Circum.
94.099"
686
Revs/Mile
673.3

How results are calculated

Tire dimensions are calculated from the metric size format (width / aspect ratio / rim diameter). Diameter, circumference, and revolutions per mile are derived mathematically — no fitment or vehicle data is used.

The 3% rule is a general reference for acceptable diameter difference, not a guarantee. Always check your vehicle manual or consult a tire professional.

How it works